Parliament House is a very odd building, even without the people who populate it: it juts out of a hill next to an artificial lake in a city of concentric circles that was purpose-built to house it. Perhaps the most scrutinised building in Australia, it is also the most secretive – but a new ABC series hosted by Canberra regular Annabel Crabb shares the secrets of the building and the people who really run it.

When the show began filming in 2016, a new set of parliamentarians were taking up residence, finding their way around the 10km of corridors, 7,482 doors and 19,000 square meetings of parquetry flooring. (“I’ve been entirely lost for the whole time I’ve been here,” the Labor MP Linda Burney tells Crabb in the first episode, with not a small amount of panic in her eyes.)

The six-part series premieres next week. Ahead of it, Crabb shares some of her favourite discoveries.

1. Sandy McInerney: queen of the underground

You would never have heard of this woman but she controls pretty much everything that comes into Parliament House (apart, of course, from elected MPs. That would be anti-democratic).

According to Sandy McInerney, the loading dock is ‘the mouth and arse of this place’. Photograph: ABC

Sandy runs the loading dock, an underground entrance where every delivery has to be x-rayed; milk, pot plants, furniture, newspapers – you name it. Sandy describes it, with characteristic bluntness, as “the mouth and arse of this place” and reckons that if she wanted to shut parliament down she’d just stop deliveries of coffee and toilet paper.

Sandy used to be in the army and was General Peter Cosgrove’s driver for 10 years. She is adopted, and went in search of her birth mother after hearing Julia Gillard’s speech about forced adoptions in Australia.

I know this sounds like the worst kind of TV tease … but you seriously will not believe who Sandy’s mother turned out to be.

2. Maria Ljubic: head cleaner, once mistaken for the Queen

Maria Ljubic is a famous face around the building these days. Photograph: Michelle Hazell/Auspic

Maria is the head cleaner at Parliament House. She has worked there since the building opened. In fact, she was on the scene when the Queen came to open the building in 1988; she dashed out with a vacuum to clean up the red carpet immediately before the event was due to start and was briefly mistaken for the monarch, earning a huge cheer.

Maria’s a famous face around parliament these days, and seems to be there all hours of the day. Having begun working at Parliament House when she was quite a new immigrant with hardly any English, she is kind of an in-house embodiment of our multicultural society. She knows every inch of the building and every cleaning hack there is. For instance: the marble foyer has to be mopped nightly with distilled water.

3. The coat of arms: very, very visibly male

Designed by Robin Blau, the stainless-steel coat of arms that sits up above the main entrance to Parliament House is part of the place’s furniture now. It’s the image I think of when I think “coat of arms”.

Unfortunately, I can never look at it in the same way again, since Parliament House’s art curator, Justine van Mourik (a wonderful woman whom I will kill for her job when I get an opportunity, and who lives deep down in the parliamentary underground in a temperature-controlled art vault full of treasures), told me the back story.

Robin Blau’s Coat of Arms (1986-87) at the main entrance to Parliament House. Photograph: ABC

When the building was under construction, the coat of arms was put out to tender. One famous Australian artist who put in a design had it rejected on the grounds that the kangaroo was “not visibly male”. Apparently this is a thing.

And when you glance at the successful design, you see that Blau definitely fulfilled that particular design specification. Yikes.

4. The basement cathedral: the bit where they ran out of money

The basement of Parliament House is one of its best-kept secrets. There are 1,100 rooms down there, teeming with a workforce who in the bad old days used to be called “the troglodytes”.

Carpenters, mechanics, cooks, laundry workers, broadcast technicians and even a stonemason (Parliament House has its own stonemason!) work down there, behind mysterious doors that lead off underground streets along which electric cars buzz all day. And behind one of the doors – I doubt I could find it again unguided – is a plant room that leads to another door that leads to … a vast, empty, unfinished space. It’s seriously the size of a cathedral, and that’s what it’s called.

It’s a bit of Parliament House they meant to finish, but ran out of money. So now it’s just a big empty cavern with a dirt floor, strewn with rubble. It’s the weirdest thing.

‘It’s the weirdest thing’: the ‘cathedral’ in the basement of Parliament House Photograph: ABC

But I also really like the fact that in this beautifully designed building, that houses a parliament governed by standing orders and procedure and centuries-old convention, there still exists a spot where you can see the earth beneath.

5. The flag: terrifyingly high maintenance

I know this is a very obvious part of Parliament House and not even an optimistic film-maker could ever claim to be “discovering” it. But the sheer rigmarole involved in keeping that sucker flying is impressive.

First: there isn’t just one flag. There’s a dozen of them, and they get changed over on the first Wednesday of every month because it’s so windy up the top of the 81-metre flagpole that the flags get shredded really quickly.

It’s tricky to get up there. Jason and Dave – two of the building’s maintenance staff – have to pack into a tiny, coffin-sized box which gets hauled up one of the stainless steel masts. It’s truly hair-raising.

To change the flags each month, two of the building’s maintenance staff have to ‘pack into a tiny, coffin-sized box’ which gets hauled up the 81-metre flagpole. Photograph: Auspic

When the flags come down each month, they go off to be patched and re-hemmed. So when you look at these things up close (and they’re giant, 13 metres by six metres) they are a jigsaw of patches and repairs. I love that. It reminds me of what democracy is like: perfect from a distance, messy up close.

• The House with Annabel Crabb premieres on 8 August at 8pm on the ABC